CdTe Quantum Dot/Dye Hybrid System as Photosensitizer for Photodynamic Therapy

We have studied the photodynamic properties of novel CdTe quantum dots—methylene blue hybrid photosensitizer. Absorption spectroscopy, photoluminescence spectroscopy, and fluorescence lifetime imaging of this system reveal efficient charge transfer between nanocrystals and the methylene blue dye. Near-infrared photoluminescence measurements provide evidence for an increased efficiency of singlet oxygen production by the methylene blue dye. In vitro studies on the growth of HepG2 and HeLa cancerous cells were also performed, they point toward an improvement in the cell kill efficiency for the methylene blue-semiconductor nanocrystals hybrid system

Effect of surface plasmon resonance in TiO2/Au thin films on the fluorescence of self-assembled CdTe QDs structure

The exceptional properties of localised surface plasmons (LSPs), such as local field enhancement and confinement effects, resonant behavior, make them ideal candidates to control the emission of luminescent nanoparticles. In the present work, we investigated the LSP effect on the steady-state and time-resolved emission properties of quantum dots (QDs) by organizing the dots into self-assembled dendrite structures deposited on plasmonic nanostructures. Self-assembled structures consisting of water-soluble CdTe mono-size QDs, were developed on the surface of co-sputtered TiO2 thin films doped with Au nanoparticles (NPs) annealed at different temperatures. Their steady-state fluorescence properties were probed by scanning the spatially resolved emission spectra and the energy transfer processes were investigated by the fluorescence lifetime imaging (FLIM) microscopy. Our results indicate that a resonant coupling between excitons confined in QDs and LSPs in Au NPs located beneath the self-assembled structure indeed takes place and results in (i) a shift of the ground state luminescence towards higher energies and onset of emission from excited states in QDs, and (ii) a decrease of the ground state exciton lifetime (fluorescence quenching).Financial support from the European Science Foundation (ESF) through PLASMON-BIONANOSENSE programme and Portuguese Foundation for Science and Technology (FCT) and FEDER through Projects PTDC-FIS-113199-2009 and PEst-C/FIS/UI0607/2013 are gratefully acknowledged. DM, DS and YR acknowledge support from Project FIS2013-41184-P of the Spanish Ministry of Economy and Competitiveness MINECO

Plasmonic Control of Radiative Properties of Semiconductor Quantum Dots Coupled to Plasmonic Ring Cavities

In recent years, a lot of effort has been made to achieve controlled delivery of target particles to the hotspots of plasmonic nanoantennas, in order to probe and/or exploit the extremely large field enhancements produced by such structures. While in many cases such high fields are advantageous, there are instances where they should be avoided. In this work, we consider the implications of using the standard nanoantenna geometries when colloidal quantum dots are employed as target entities. We show that in this case, and for various reasons, dimer antennas are not the optimum choice. Plasmonic ring cavities are a better option despite low field enhancements, as they allow collective coupling of many quantum dots in a reproducible and predictable manner. In cases where larger field enhancements are required, or for larger quantum dots, nonconcentric ring-disk cavities can be employed instead

Computer Modeling the Excitonic Reflection and Photoluminescence Spectra of GaN Epitaxial Layers

Photoluminescence (PL) and reflection excitonic spectra o f GaN single layer grown on sapphire substrate by MOVPE were modeled with aim to estimate a basie parameters o f free A- and B- excitons. The calculations were performed in the frame o f two-oscillator model for dielectric function e(E). Three layered model o f crystal was used for fitting o f reflection spectrum which was measured at T=80K. In this way the dead layer thickness d=6 nm, resonance energies Eа=3.4916 eV and Eв = 3.5008 eV as well as the broadening parameters Га = 5.27 meV and Гв = 7.14 meV of the free excitons were obtained. These parameters were used then for fitting of PL spectra in assumption o f the thermal equilibrium for excitons taking into account the self-absorption of resonance emission. The values of diffusion coefficients Dа =0.3 cm²/s, Dв = 0.1 cm²/s and exciton lifetimes Ƭa = 37 ps, Ƭв = 17 ps were estimated

Иммобилизация РАО в перовскитоподобную матрицу

Выпускная квалификационная работа с., рис., табл., источников, прил. Ключевые слова: перовскит, иммобилизация радиоактивных отходов, самораспространяющийся высокотемпературный синтез, матричные материалы Объектом исследования является иммобилизация радиоактивных отходов в матричный материал методом СВС на основе перовскита. Цель работы – получение химически устойчивой матрицы для иммобилизации актиноидной фракции радиоактивных отходов методом СВС В процессе выполнения магистерской диссертации отработана технология получения матричного материала методом СВС. В результате исследования были определены закономерности образования фаз состава матриц. Степень внедрения: организация технологического процесса иммобилизации актиноидной фракции радиоактивных отходов методом СВС Область применения: атFinal qualifying work with., Fig., Tab., Sources, adj. Keywords: perovskite, radioactive waste immobilization, self-propagating high-temperature synthesis, matrix materials The object of research is the immobilization of radioactive waste in the matrix material by the SHS-based perovskite. The purpose of work - to obtain a chemically stable matrix for the immobilization of actinide fraction of radioactive waste by SHS In carrying out the master's thesis the technology of producing the matrix material by SHS. The study of the formation of the composition of the matrix phase have been identified. Degree of implementation: the organization of the process of immobilization actinide fraction of radioactive waste by SHS Scope: the nuclear industry

Electron-phonon interaction effects in semiconductor quantum dots: a non-perturbative approach

Multiphonon processes in a model quantum dot (QD) containing two electronic states and several optical phonon modes are considered by taking into account both intra- and nterlevel terms. The Hamiltonian is exactly diagonalized, including a finite number of multiphonon processes large enough to guarantee that the result can be considered exact in the physically important energy region. The physical properties are studied by calculating the electronic Green’s function and the QD dielectric function. When both the intra- and interlevel interactions are included, the calculated spectra allow several previously published experimental results obtained for spherical and self-assembled QD’s, such as enhanced two-LO-phonon replica in absorption spectra and up-converted photoluminescence to be explained. An explicit calculation of the spectral line shape due to intralevel interaction with a continuum of acoustic phonons is presented, where the multiphonon processes also are shown to be important. It is pointed out that such an interaction, under certain conditions, can lead to relaxation in the otherwise stationary polaron system.Fundação para a Ciência e a Tecnologia (FCT

Template dissolution interfacial patterning of single colloids for nanoelectrochemistry and nanosensing

Deterministic positioning and assembly of colloidal nanoparticles (NPs) onto substrates is a core requirement and a promising alternative to top-down lithography to create functional nanostructures and nanodevices with intriguing optical, electrical, and catalytic features. Capillary-assisted particle assembly (CAPA) has emerged as an attractive technique to this end, as it allows controlled and selective assembly of a wide variety of NPs onto predefined topographical templates using capillary forces. One critical issue with CAPA, however, lies in its final printing step, where high printing yields are possible only with the use of an adhesive polymer film. To address this problem, we have developed a template dissolution interfacial patterning (TDIP) technique to assemble and print single colloidal AuNP arrays onto various dielectric and conductive substrates in the absence of any adhesion layer, with printing yields higher than 98%. The TDIP approach grants direct access to the interface between the AuNP and the target surface, enabling the use of colloidal AuNPs as building blocks for practical applications. The versatile applicability of TDIP is demonstrated by the creation of direct electrical junctions for electro- and photoelectrochemistry and nanoparticle-on-mirror geometries for single-particle molecular sensing

Photonic molecules and spectral engineering

This chapter reviews the fundamental optical properties and applications of pho-tonic molecules (PMs) - photonic structures formed by electromagnetic coupling of two or more optical microcavities (photonic atoms). Controllable interaction between light and matter in photonic atoms can be further modified and en-hanced by the manipulation of their mutual coupling. Mechanical and optical tunability of PMs not only adds new functionalities to microcavity-based optical components but also paves the way for their use as testbeds for the exploration of novel physical regimes in atomic physics and quantum optics. Theoretical studies carried on for over a decade yielded novel PM designs that make possible lowering thresholds of semiconductor microlasers, producing directional light emission, achieving optically-induced transparency, and enhancing sensitivity of microcavity-based bio-, stress- and rotation-sensors. Recent advances in material science and nano-fabrication techniques make possible the realization of optimally-tuned PMs for cavity quantum electrodynamic experiments, classical and quantum information processing, and sensing.Comment: A review book chapter: 29 pages, 19 figure